The present invention relates to a method of detecting a film with an optical detector in a photographic processing machine.
A photographic processing machine, e.g. a photographic printer, is provided with an optical film detector which, upon detecting the loading of a film, produces and delivers a detection signal to other automatic devices for actuation.
The film detector is preset to an appropriate detection condition level by an initial setting of reference data using a developed film. The initial setting is made to between two extreme levels which represent the presence and absence of the film. In common, the initial setting is carried out at the factory before shipment and/or at the site by a service person during maintenance service.
Such a conventional film detecting method is thus essential to conduct the initial setting using a reference film. If the film detector comprises a plurality of components, the initial setting will be troublesome because the components have to be adjusted one by one.
Also, a reference film with an average density should be employed. If a high density film is used for the initial setting, the detection of a low density film is hardly feasible. The photographic printer machine may thus produce frequent faulty operations or troubles.
The initial setting also tends to deteriorate with time and becomes incorrect, for example, when the film detector gets dirty.
It is an object of the present invention, for eliminating the foregoing disadvantages of the conventional film detecting method, to provide an improved film detecting method in which the initial setting is carried out without using a reference film so that no troublesome adjustment on each component is needed and faulty operations of the film detector are avoided.